Improving the transmission error source tracing method for gear hobbing machines

By considering the uncertainness of initial measuring position of encoders and signal sidebands caused by the fault gear pair, this paper presented a new comprehensive harmonic analysis method for the transmission error of gear hobbing machine. Based on that, a test platform was established, in which two circle grating encoders were connected to the hob spindle and workpiece spindle respectively. With the help of this new harmonic analysis method as well as the self-developed test platform, a new improved transmission error fault diagnosis method was developed for the gear hobbing machines. To verify its accountability, a case study was conducted on a YS-type gear hobbing machine. According to the spectrum amplitude comparison and the analysis of harmonic frequency distribution, the fault transmission gear pair was successfully located. This improved transmission error source tracing method was very helpful for quantifying both the manufacturing qualities and assembly qualities of parts and locating potential error source for new gear hobbing machines.

Approach for multiscale modeling the thermomechanical tool load in gear hobbing

In this report, an approach is presented how a geometric penetration calculation can be combined with FE simulations to a multiscale model, which allows an efficient determination of the thermomechanical load in gear hobbing. FE simulations of the linear-orthogonal cut are used to derive approximate equations for calculating the cutting force and the rake face temperature. The hobbing process is then simulated with a geometric penetration calculation and uncut chip geometries are determined for each generating position. The uncut chip geometries serve as input variables for the derived equations, which are solved at each point of the cutting edge for each generating position. The cutting force is scaled according to the established procedure of discrete addition of the forces along the cutting edge over all individual cross-section elements. For the calculation of the temperature, an approach is presented how to consider a variable chip thickness profile. Based on this, the temperature distribution on the rake face is calculated. The model is verified on the one hand by cutting force measurements in machining trials and on the other hand by an FE simulation of a full engagement of a hob tooth.

Comparative LCA of Automotive Gear Hobbing Processes with Flood Lubrication and MQL

The Life Cycle Inventory (LCI) data of a gear hobbing was obtained by means of the methodology Unit Process Life Cycle Inventory (UPLCI), in order to conduct a comparative Life Cycle Assessment (LCA) between hobbing assisted by Flood Lubrication (FL) and Minimum Quantity Lubrication (MQL). The results of the LCIA pointed out 4 among 11 normalized environmental impact categories totalized more than 80% of the accumulated impacts: fossil depletion (43%), climate changes (19%), terrestrial acidification (11%) and freshwater consumption (8%). The identified hotspot in the case study was the input flow of raw material for the system “Hobbing Machine”, which was linked to more than 75% of the total amount of normalized potential environmental impacts. Once, changes on raw material depends on the gear design, the research focused on the environmental aspects of energy and cutting fluid consumption, which depends directly on the hobbing process parameters. The introduction of MQL provided reduction of 70.77% on the total amount of normalized potential environmental impacts, while the strategies to reduce electric energy consumption by the machine tool accounted only for 3.74%. The consumption of energy and cutting fluids are the main environmental aspects of the gear hobbing process itself, since they are directly associated to the majority of potential environmental impacts derived from that machining operation. Nevertheless, when raw material flow is taken into account in the LCA, it turns into the process hotspot, due to high energy demanded in the steel-making process, forging and turning operations to shape the semi-finished gear.